Mac (but not PC) slow on wifi

I have an aluminum Macbook on a wireless network. My network is configured as follows:
DSL <--> Netgear Router <-Ethernet-> Netgear Router set up as an access point*

In the area covered by the AP, I have the Macbook and an old, busted PC. The PC works fine, and internet is as fast as if it was plugged in. The mac says it has full signal, but the internet speed varies greatly. This Macbook tends to show full bars even when the signal is weak, though. Sometimes it loads pages fast, sometimes, it takes almost a full minute to load pages. While I haven't tested it on many other networks, it appears to work fine elsewhere. Anyone have any idea what the problem is? It's almost as if the Macbook isn't connecting to the AP and is connecting straight to the main router which is far away. As I was typing this post, the Macbook completely lost wifi signal.

On both the mac and PC if i traceroute 192.168.1.1 it only shows one hop. It doesn't show a hop through the AP at 192.168.1.254, but I'm not sure if it should, especially since the working pc doesn't show the hop either.

Btw, my iPhone appears to be working fine on the network, though I'm not sure how much of a speed difference I'd really notice on the phone anyway.

*Turned off DHCP, set same SSID and password, plugged in to main router with ethernet cable connected to LAN ports on each (I'm fairly sure that they are new enough to not need crossover. If that was the problem, nothing would connect at all, right?) . The main router sees the AP in connected devices.

Yea, getting close to the router works. But the PC appears to be using the AP. It has excellent coverage until i turn off the AP, then it loses wifi or goes to very low signal.

Now I'm even more confused. I turned off the radio on the main router, leaving the router/access point as the only one with the radio on. Even though it is 6 inches from the computer, the connection is still unreliable. I can tell no difference form when the main router is plugged in, so it isn't a problem of the macs not seeing the close one and connecting to the far away one.

btw, I have more test machines now. I brought my white macbook, and it is at least as slow, maybe slower, than the aluminum one. Same story with a Powerbook G4. I have two iPhones available (3g and 3gs) both work perfectly. PC still works perfectly. Does this mean I should try a different router down here? If so, what do y'all recommend? I don't think it makes sense to buy an airport just to act as an AP. What routers (brand and model) have y'all had the most success with? Since we are on DSL with old computer that only use wireless-g, n is optional.

Thanks y'all!
gsfgf

I'll be over there tomorrow and can mess with it, but I know it's set to the default channel setting. IIRC, it's auto or something like that. Is there a way to tell what channels are the less trafficked. I can't see any other wifi networks in the airport drop down list, but that doesn't mean there's not phone traffic, etc. right?

They were both set to auto, and the main one was using channel one and the other one was using channel 6. Should the both be on the same channel? I set it up that way; I'll see if that helps.

btw, istumbler didn't see any other networks.

UPDATE: I put both routers on channel 5 (istumbler eventually found ones on six and one) as well as added the other DNS servers ad the problems appear solved. Reliable, fast wifi for almost a week.

Thanks for all the help!